[sweetyee]

I'm doing a leaching test on waste material in a bucket of 20L distilled water using aeration (100% v/v) for next 6 weeks. On daily basis, I will be taking out 100 mL from the bucket for analysis. How do i maintain the 20 L (100%v/v) when the water level will drop due to daily sampling and possibility of evaporation without affecting the accumulated concentration of leached out solute that would be analyzed?

[curiouscat]

If the leached material is non volatile none will be lost to evaporation.

Then it's a matter of mathematical adjustment. Keep topping up to 20 L after drawing each sample and then

c in gm / L

c1'= c1

c2' = ( c2 * V2  + 0.100 * c1 ) / 20

c3'= (c3 *V3 + 0.1 * (c1 + c2 ) ) / 20

etc. (not sure if my math is right)

[Hunter2]

You can add again 100 ml DI-Water to keep the volume. The next analysis you can calculate to 1,9 l.

[sweetyee]

Thanks. My other concern is on the diluted concentration of the analyzed analyte from water top up. Would it advisable not to top up the water after each withdrawal? But i am worried that the concentration does not represent the actual leached amount since lesser water means it will be more concentrated. Can this diluted/concentrated factor due to water top up/withdrawal be ignored since concentration changes in general but not in the true amount of leached material? Pl advise.